Modern motor vehicles are often equipped with vehicle movement dynamics control systems such as an ESC (Electronic Stability Control) system which can selectively influence the driving behavior of a motor vehicle. In order to ensure driving stability, i.e. make sure that the vehicle follows the driver's prescriptions, in this context automatic wheel-specific braking forces can be generated and/or the drive torque reduced. The control intervention is derived directly from the driver's inputs (steering, braking, opening the throttle) and takes place in a reactive fashion, wherein an input by the vehicle movement dynamics control does not take place until the driving behavior deviates by a measurable absolute value from the driver's request which is calculated on the basis of a vehicle model. An active vehicle movement dynamics control system is known, for example, from EP 0 792 229 B, which is incorporated by reference.
An increase in the driving safety through proactive or predictive control interventions can take place on the basis of a surroundings sensor system (radar and/or optical cameras) which permits controlling the distance from a vehicle traveling ahead (ACC: Adaptive Cruise Control), the triggering of emergency braking when obstacles are detected (EBA: Emergency Brake Assist) or permits warnings or interventions when lane boundaries are crossed (LDW: Lane Departure Warning).
Currently, approaches for providing a driver with early warning about potentially hazardous bend situations (CSW: Curve Speed Warning) are being trialed. Information about a bend lying ahead is determined by means of digital maps, such as, for example, the geometric characteristic. In this context, the actual position of the vehicle (ego position) is determined on the basis of satellite navigation (GPS: Global Positioning System), solely or in conjunction with an inertial sensor system or inertial navigation system by means of an electronic control device (IPC: Inertial and Position Cluster). Such CSW systems warn the driver if he is approaching a bend too quickly.
For example, DE 10 2009 041 580 A1, which is incorporated by reference, discloses a method for predictively warning about bends, in which method the bend profile is detected by means of surroundings sensors, in particular beam sensors and/or cameras, and is compared with a bend profile based on digital map information, on the basis of which a bend verification signal is generated. A bend warning signal is generated and output as a function of the bend verification signal.
EP 1 805 530 B1, which is incorporated by reference, discloses a method for increasing the driving safety and/or comfort of a motor vehicle in which data from a vehicle control device, which is provided for controlling a safety-increasing function, is logically linked to data of a navigation device or cartographic data, wherein cartographic data is used together with information, acquired directly or indirectly in the vehicle by sensors, relating to the current driving state in order to determine a current hazard value, and wherein interventions into the function groups with safety-increasing functions occur in accordance with the hazard value, wherein, in particular, a visual, acoustic or haptic warning to the vehicle driver is issued in addition to or instead of the intervention.
The coefficient of friction of the road is a decisive parameter for CSW systems or generally for vehicle movement dynamics control systems. For example, it determines the maximum speed at which a bend can be travelled through since it limits the transmissible forces. The coefficient of friction depends on the pairing of the tire on the road and therefore on the instantaneous ambient conditions and is therefore generally not known. A faulty estimation of the coefficient of friction—or even the fundamental adoption of a high coefficient of friction—results in a large risk for the vehicle manufacturer or supplier because an excessively high recommended speed (about which a warning is not given) can lead to recourse claims arising from product liability.